Considering the Cross-Cultural Prevalence for Unipolar Depression and Bipolar Disorder

Considering the cross-cultural prevalence for unipolar depression and bipolar disorder, the rates are

A) more variable across cultures for unipolar depression.
B) more variable across cultures for bipolar disorder.
C) similarly invariable for both disorders across cultures.
D) highly variable for both disorders across cultures.
E) increasing in their variability over time for both disorders.